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I make meringue cookies frequently. Here are the things I've learned. (We call them white cookies. Here's the recipe: http://food52.com/recipes...)

I don't use cream of tartar or vinegar. I think they change the taste--and not in a good way. I beat the egg whites (no yolks! Be anal about it!) with a pinch of (morton's) kosher salt until they start to stiffen and whiten. Then I add the sugar, beating till the meringue is smooth and glossy, and stiff peaks form when you raise the beaters. Finally, when you make the cookies, put them into a pre-heated 350 degree oven and turn the oven off, or down to the lowest temperature, for about 3 hours. That way you are drying the meringues, not baking them. In my old house I had a new electric oven that held its temperature well so i turned the oven off. In this house I have a very temperamental gas oven, so I preheat it while I'm making the meringues and then turn the temperature down to the lowest setting (170 in my case). The cookies are ready to come out in about 3 hours, and they are still shiny and white. i hope this helps.